Physical properties of the TCNQ salts with 1‐methyl‐3‐alkylimidazolium derivatives

Abstract

AbstractElectrical conductivity and spectral properties (UV–VIS absorption and temperature dependence of IR absorption) are studied in the series of 1‐methyl‐3‐alkylimidazolium (MRI+) 7,7′,88′–tetracyano‐p‐quinodimethanes \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm (TCNQ)}^{\mathop {\rm - }\limits_{\rm .} } $\end{document} in the form of simple and complex salts. The poor electrical conductivity of simple salts (10−4 to 10−7 Sm−1) is influenced by the dimer arrangement of \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm TCNQ}^{\mathop {\rm - }\limits_{\rm .} } $\end{document} stacks. The magnitude of the gap energy Eg, (between 1.0 and 1.2 eV) depends on the size of the donor. Combining these salts with neutral TCNQ0 molecules gives complex salts with electrical conductivities increased by 3 to 7 orders of magnitude. Eg decreases to 0.4 to 0.5 eV, which is in a good agreement with 0.4 eV obtained from IR measurements. The electrical conductivities of 1‐methyl‐3‐propylimidazolium (MPI), 1‐methyl‐3‐butylimidazolium (MBI), and poly‐(1‐methyl‐3‐allylimidazolium) (MPaI) complex TCNQ salts are also influenced by the donor level located about 0.05 to 0.06 eV below the conduction band.